Sensor alignment detection method for an infrared blind-zone sensing system

Abstract

A diagnostic method for a blind-zone sensing system including leading and trailing passive IR sensors periodically determines a separation distance between coverage areas of the leading and trailing sensors to diagnose sensor alignment. Signals produced by the leading and trailing sensors are sampled and stored over a defined interval of time for processing. A condition in which the sensor coverage areas abruptly encounter a stationary region of cooler temperature is detected when corresponding signal deflections are identified. The elapsed time between the identified signal deflections is measured and used along with an accurate measure of the vehicle speed to compute the separation distance between coverage areas of the leading and trailing sensors.

1. An alignment detection method for a sensing system of a motor vehicle, the sensing system having first and second passive sensors mounted on the vehicle and aligned to detect radiant energy in first and second coverage areas laterally spaced from the vehicle and longitudinally separated by a predetermined distance for purposes of sensing an object of interest, the alignment detection method comprising the steps of:
 sampling and storing first and second signals produced by said first and second sensors; 
 monitoring the sampled signals to identify deflections of said first and second signals that are indicative of a change in detected radiant energy caused by a stationary object or region; 
 determining a time difference between occurrences of the identified deflections of said first signal and second signals; 
 calculating a distance using said determined time difference and a measured speed of said vehicle; and 
 comparing said calculated distance to said predetermined distance to determine if said first and second passive sensors are properly aligned. 
 
   
   
     2. The method of  claim 1 , including the step of:
 calculating said distance according to a product of the determined time difference and the measured speed of said vehicle. 
 
   
   
     3. The method of  claim 1 , including the step of:
 determining that said first and second passive sensors are properly aligned when a deviation of said calculated distance from said predetermined distance is less than a reference value. 
 
   
   
     4. The method of  claim 3 , including the step of:
 using said calculated distance for purposes of sensing said object of interest. 
 
   
   
     5. The method of  claim 1 , including the step of:
 determining that said first and second passive sensors are mis-aligned when a deviation of said calculated distance from said predetermined distance is greater than a reference value.